The tips of the cusps of the teeth form a curve from the front to the back of the mouth. This anterior-posterior curve is called the curve of Spee. The same cusps form a curve from the right to the left, or across the mouth, called the curve of Wilson. By convention, these curves do not include the six (6) anterior teeth (which normally overlap upon occlusion). So, these curves are defined as beginning at the distal aspect of the cuspid or canine tooth.
In planning the reconstruction of a dentition, with either crowns, or fixed or removable partial dentures, or complete dentures, these curves must be analyzed and modified to eliminate any trauma to a tooth, or group of teeth, both in vertical position and lateral movements.
If a line is drawn across the cusp tips of the posterior or back teeth, it forms an arc or a portion of a circle that can be measured as the radius of that circle, this radius normally may vary from a three inch radius to an essentially flat surface. It is historically evaluated, by trial and error archial analysis with calipers or exotic, expensive analysis equipment.
In restorative dentistry, elongating, shortening or extracting a tooth, or teeth, may be necessary to prevent the opposing tooth or teeth from locking, tripping, or causing trauma to the teeth, supporting structures and joint.
The use of templates is a quick, simple, economical system of diagnosing curves, and establishing cusp height in the course of fabricating crowns, inlays, bridges, partials and full dentures.